Let’s cut to the chase, with three of the many reasons to see Catherine Trieschmann’s “One House Over,” the best of the 10 world premieres at the Milwaukee Repertory Theater during Mark Clements’ eight years as artistic director (Clements also directs this production).

First, it takes on the thorniest of current political issues — immigration — in ways that are provocative but not preachy. Second, it’s laugh-out-loud funny, as was clear from watching Friday’s opening night audience. Third, Clements’ magnificent five-actor cast expertly mines the subtext of a play that’s also about being lonely and isolated in a divided America.

As things get underway — in the backyard of a modest but solid home in a first-ring Chicago suburb — fiftysomething Joanne (Elaine Rivkin) is hiring thirtysomething Camila (Zoë Sophia Garcia) to care for Milos (Mark Jacoby), her ailing and cantankerous 89-year-old father who's also a first-generation Czech immigrant.

Divorced, alone and scratching out a living as a violin teacher, Joanne needs the help. Rivkin also immediately makes clear how unsettled Joanne feels asking for it — and thereby placing a woman she doesn’t know in the position of surrogate daughter. Especially when Camila and husband Rafa (Justin Huen) will be living with her, in a basement apartment.

It’s almost immediately clear to us — and Joanne — that Camila and Rafa are undocumented. Good liberal that she is, Joanne looks the other way. Good white liberal that she is, she also wallows in self-conscious guilt involving her privilege — while doing little about it, other than mouthing cheerleading platitudes involving Barack Obama (the play is set in 2010).

Like Joanne, each of these characters, as well as Patty the nosy neighbor (Jeanne Paulsen), initially play as types; particularly before intermission, the resulting humor goes broad and suggests a well-made sitcom, enacted by actors whose comic timing is impeccable. It’s been a long time since I’ve heard an opening night Rep audience laugh this spontaneously and hard.

But as relationships develop and unexpected affinities emerge — between Camila and the irascible, sometimes racist Milos, and between Joanne and Camila’s alternately mischievous and ambitious husband — psychological boundaries get crossed, suggesting characters who are more textured and conflicted as well as far less predictable than they’d initially seemed.

That makes for some two-actor scenes that can be heartbreakingly poignant; it also reveals fault lines that can be ugly. But it primarily underscores the loneliness these five characters share.

Four of them miss a past they remember as better. All of them are displaced from the lives they’d imagined. And all of them feel adrift and vulnerable in a world that’s let them down — longing, as a song they’ll sing goes, for someone to show them the way home.

“One House Over” continues through March 25 at the Quadracci Powerhouse Theater, 108 E. Wells St. For tickets, visit milwaukeerep.com. Read more about this production at TapMilwaukee.com.

PRODUCTION NOTES

Catherine Trieschmann: I’ve now read and/or seen four of Trieschmann’s plays, including the Rep production of “How the World Began” five years ago. All of them involve a conceit that brings people from very different perspectives together, forcing strangers who might never ordinarily cross paths to engage each other, often with surprising results. I haven’t always bought those conceits. But I’ve consistently been drawn in by the ensuing explorations — undertaken with wit, verve and courage — of how we might mediate our differences. Those explorations are all the more impressive because such mediation in Trieschmann’s work remains open-ended and incomplete; Trieschmann has too much respect for the integrity of her characters, regardless of their perspective, to suggest their differences will ever entirely disappear.

There are things I liked about each of these plays (the others, for the record, are “Crooked” and “The Most Deserving”; Trieschmann has written a few more that I haven’t read or seen). But “One House Over” is the best of them. It has legs and will travel, beyond its next scheduled stop in Rochester, N.Y. (this current production is being co-produced with Rochester’s Geva Theatre Center). And it all began here, in Milwaukee, because of a conversation between Clements and Trieschmann. Hold that thought and read on.

Revisions: In January, I’d read the prerehearsal version of Trieschmann’s script; it was already quite good. But I was continually, pleasantly surprised Friday night by how much better it now is after an intense rehearsal process, much of it attended by Trieschmann herself. Dialogue that played cute is gone. Backstories are sharper. Characters’ underlying vulnerabilities are more apparent. The reworked final scene is now quietly devastating. There are a few places, particularly involving overtly political references to Obama, where additions (as well as what was already in the script) hit the nail too hard; hopefully, these will be pruned. Because Rivkin is so good at conveying the welter of contradictions involving white liberals, as refracted through Joanne’s own bundle of insecurities and hungers, these broad brushstrokes are unnecessary. But that’s a quibble. This is a good script.

Acting: That script is made stronger still in this premiere production by Clements’ strong directing and cast. Rivkin, as suggested, can be achingly vulnerable and insecure, as she charts the choppy waters confronting any singleton living alone when well into middle age. Joanne just wants to be held; Rivkin makes one want to vault onto the stage and oblige. Jacoby is a marvel as Milos: Even when he’s most indefensibly irascible and noxious, Jacoby suggests that this curmudgeon is goodhearted; he acts out because he’s lonely and wants attention. Even when she says nothing, Garcia speaks volumes about the hardships (and the boredom) endured by any caretaker; she conveys even more as Camila longs for home, while expressing the wary dis-ease of one who continually feels watched. Even when Rafa seems blinded by his single-minded ambition to move up, Huen never lets us forget that it’s related to his correlative quest for dignity as a husband and a man, proudly trying to stand tall even as we watch him continually cut down. Saddled with the toughest role of all as the quirky Patty, Paulsen sketches a character whose brusque manner conceals a smart and lonely woman’s unmet need for friends. Her idiosyncrasies are both her armor and the result of her isolation.

“Native Gardens”: In its theme, structure and tone, Trieschmann’s play reminds me of Karen Zacarías’ “Native Gardens,” a play we’ll see next season at Renaissance Theaterworks under the direction of Marti Gobel. Both plays are set in a backyard (adjoining backyards, in Zacarías’ play), the contours of which become an additional flashpoint in conflicts that are all about immigration and difference, how we define what it means to be an American and what that says of who we are as people. Both plays are broadly funny. Both plays deploy humor to disarm audiences, enabling a hard look at a contentious political topic on terms that remain engaging and multidimensioned. In both plays, the immigrant couple is also younger, adding an additional fault line. I liked “Native Gardens” when I saw it last summer in Chicago; I’m glad it’s coming here and that it’s receiving multiple productions. All by way of saying that “One House Over” deserves the same and then some. It’s a better play: funnier, deeper, more conflicted and more honest, right through its much more credible and dramatically effective ending.

The Rep’s New Play Initiative: Even as the lights were coming up on the opening scene of Trieschmann’s play Friday night, the Rep was announcing the latest coup in its fabulous new play initiative: Clements and Brookfield Central High grad Ayad Akhtar — an internationally renowned and Pulitzer-winning playwright — will collaborate on a world premiere adaptation of Akhtar’s debut novel, “American Dervish.” The Rep is also staging the regional premiere next year of Akhtar’s play “Junk,” which will revisit the corporate takeovers of the 1980s with one of largest casts to appear on a Rep stage in the past decade.

This world premiere of an Akhtar play — a very big deal that’s likely to attract press coverage and critics from around the country — is made possible by the same new play initiative that allowed the Rep to commission and launch “One House Over.” I’ve spilled a lot of ink in this paper in praise of Clements’ passionate commitment to new plays — something that’s been a topic of our conversations (and a focus of his) since he came to Milwaukee nearly a decade ago. That same initiative has also included a reading series — launched late last year — in which the Rep regularly profiles new work, both by writers under commission and by other playwrights in whom the Rep is interested. I’ve attended three of the first four public readings, emerging from each one with an enlivened sense of all theater can do. You can learn more about the Rep’s reading series and new play initiative, including the dates of upcoming readings, here.